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(5 BYA) Beginning of the Solar System and the Sun
During this time period the sun was formed by dust and other particles gravitating towards each other. The solar system had consisted of mostly dust, and swirled aroung the sun.
The formation of the sun and the swirling dust in the solar system let to the formation of the solar system that we know today, with its 8 planets. -
(4.6 BYA) Growing of the Earth's size
Similar to the method that the sun had formed, the swirling mass of dust around the sun eventually gravitated towards each other to form the Earth. The physics of gravity show that as the Earth grew larger, the gravitation force of it applied to other masses also grew. This resulted in collision of many large masses, which in turn released enough thermal energy to melt the surface of the Earth.
This allowed the earth to grow into what it is today. -
(4 BYA) Finishing touches on the Structure of the Earth
After millions of years of constant collisions, the earth and its surface had finally settled. This is because the collisions between masses released the thermal energy that melted the earth's surface, which made the structure of the earth. This allowed the transformation of this barren planet into something that looks like what it is today. -
(4 BYA) Origins of Organic Molecules
Because scientists know that the oldest rocks are around 4 billion years old, they infer that organic molecules came about during that time.
With the beginnings of organic molecules, life became possible! -
(3.5 BYA) Existence of Stromatolites
Stromatolites, or layered colonies of Lynbgya cells, probably lived during this time period. Scientist can show this because they have fossils of the stromatolites from this time. -
(3 BYA) Photosynthetic Organisms
There is evidence that certain organisms were capable of photosynthesis during this time period. This is extremely important to the future of biological organisms because this way they could create energy for their own use.
This led to the formation of plants and autotrophs. -
(2.2 BYA) Earth as we Know It
By now, after continuous melting of its surface and many collisions, the earth finally looked similar to what it does today. This means oceans, land, and plants existed. This resulted from the existence of microorganisms.
Without this, the earth would not be able sustain life, and we wouldn't exist now. -
(2 BYA) Oxygen Levels
By now the oxygen levels of the Earth were close to the levels of oxygen today. This was one of the final steps to making life possible on planet earth. -
(1.5 BYA) Aerobic Prokatyote's
Based on endosymbiosis, during this time period a type of small aerobic prokaryote was being engulfed by a larger anaerobic prokaryote. This led to the creation of mitochondria and chloroplasts. -
(1 BYA) Ozone Layer
Ozone (O3) formed – protected organisms from harmful UV rays so they could exist on land. If the ozone layer had never formed, it would be impossible for life to exist on earth. -
(1600-1700) Robert Hooke
Robert Hooke studied nature by using a basic light microscope. This led to the use of microscopes in many scientists today.
He had studied a thin layer of cork from a tree and realized that it had multiple blocks inside of it, similar to a cell in a room. This is where the term "cell" comes from, referring to the structure and basis of all living organisms. -
(1600-1700) Redi's Experiment
Redi showed that flies did not spontaneously come out of meat. He showed that there needed to be flies to make flies. This was revolutionary because it completely disproved spontaneous generation. -
(1700-1800) Spallanzani
Spallanzani tested the theory of spontaneous generation of microorganisms. His experiment showed that the theory was false. He also helped show that the "life force" that many scientists claimed was true. -
(1800-1900) Pasteur
Pasteur cleared up the controversy of spontaneous generation. His experiment used the swan neck bottle that was key to his success in dissaprooving spontaneous generation. -
(1900-Present) Thomas Cech
Thomas Cech found that a type of RNA found in some unicellular eukaryotes that is able to act as a chemical catalyst. He found that RNA is able to cut itself into smaller strand of RNA. This suggests that life could have possibly started as RNA. -
(1900-Present) Oparin
Oparin had a hypothesis that the gasses in the atmosphere during the early stages of the earth were heated up to the point that they turned to simple organic compounds. -
(1900-Present) Urey and Miller
Urey and Miller had an experiment that tested Oparin’s hypothesis. They set up an experiment that simulated the hypothetical conditions that were thought have been present at the time if the earths birth. -
(1900-Present) Sidney Fox
Sidney Fox research the physical structures that led to the first cells. He also discovered the living conditions that might have been present when life was first formed. By using volcanic material from a cinder cone, he discovered that the temperature was 100 degrees Celsius just four inches beneath the surface of the cinder cone. -
(1900-Present) Radiometric Dating
Radiometric Dating is a method that takes advantage of the radioactive decay of unstable isotopes to determine how old certain substances are. -
(1900-Present) Lynn Margulis
Lynn Margulis hypothesized that the first cells with chloroplasts started when a host organism ingested photosynthetic bacteria. Her theory alos states that mitichondria fromed from proteobacteria.
